Estimation of Loss of Recreational Value Due to Sand Beach Erosion and Effect of Adaptation Policy

Abstract

4 正会員 兵庫県立大学 環境人間学部(〒〒670-0092 兵庫県姫路市新在家本町1-1-12) 5 正会員 山形大学 人文学部(〒990-8560 山形市小白川町1丁目4-12) 砂浜侵食による対策は様々な工法を組み合わせて実施されている．しかし，これらの対策は人工構造物 や波による砂の流出に対するものであり，地球温暖化を想定した対策は検討されていない．本研究では， 地球温暖化に対する適応政策を検討する際に必要な情報の提供を目的とし，著者らの既存研究より新しい 交通網データ及び砂浜侵食の影響を用いて，仮想的な適応政策による費用対効果を算出した．具体的には， 各都道府県の砂浜を対象に，気候モデルMIROCのRCP2.6とRCP8.5のシナリオの下，砂浜侵食による被害 額を推計した．また，各都道府県の過去に行われた養浜事業の実績から，仮想的な適応政策の効果を検討 した．データの更新により，砂浜侵食の被害額の過大推計を抑えられ，また，各都道府県の養浜事業を考 慮した費用対効果となったと言える．

Cost-Benefit Analysis of Adaptation to Beach Loss Due to Climate Change in Japan

“…Sao et al [12] and Nakajima et al [13] used the future projection of beach loss by Udo et al [9] and respectively estimated damage costs for RCP2.6 and RCP8.5. Sao et al [12] estimated them as 254-284 (m.USD/year) in 2031-2050 and 426-494 (m.USD/year) in 2081-2100.…”

“…Sao et al [12] and Nakajima et al [13] used the future projection of beach loss by Udo et al [9] and respectively estimated damage costs for RCP2.6 and RCP8.5. Sao et al [12] estimated them as 254-284 (m.USD/year) in 2031-2050 and 426-494 (m.USD/year) in 2081-2100. One reason for the difference between results reported by Sao et al [12] and those of our study is that our general equilibrium approach reflects price changes and income changes that are not considered in the definition of consumer surplus derived from the partial equilibrium approach.…”

“…Sao et al [12] estimated them as 254-284 (m.USD/year) in 2031-2050 and 426-494 (m.USD/year) in 2081-2100. One reason for the difference between results reported by Sao et al [12] and those of our study is that our general equilibrium approach reflects price changes and income changes that are not considered in the definition of consumer surplus derived from the partial equilibrium approach. Consequently, it is apparent that beach loss damage costs in our study are slightly lower than those found in earlier studies.…”

“…For hypothetical adaptation measures related to beach loss, we assume that after erosion of coastal areas caused by the sea-level rise, the coastal area can be restored to its earlier state by implementation of adaptation measures such as a public works project using artificial beach enhancement. From considerations of data availability and comparison with earlier studies, we chose to use an average adaptation cost per unit area assumed by Sao et al [12] for the scenario of adaptation measures for restoring sandy beaches. Sao et al [12] collected data including those of 92 public works in 33 prefectures related to artificial beach enhancement, and assumed the average adaptation cost per unit area as 215.96 USD/m 2 from available data for sandy beaches.…”

“…From considerations of data availability and comparison with earlier studies, we chose to use an average adaptation cost per unit area assumed by Sao et al [12] for the scenario of adaptation measures for restoring sandy beaches. Sao et al [12] collected data including those of 92 public works in 33 prefectures related to artificial beach enhancement, and assumed the average adaptation cost per unit area as 215.96 USD/m 2 from available data for sandy beaches. However, since few public works projects are limited to artificial beach enhancement and since these projects include costs of protecting land unrelated to sandy beaches, it is noteworthy that the average adaptation cost that we assumed might be overestimated.…”